Study and analysis of passage planning principles. Voyage planning and monitoring from Sakai to Point Fortin

Proper bridge procedures, team management and voyage planning are the most important principles to achieve the safest and most effective navigational passage from berth to berth. A significant percentage of maritime accidents and casualties are associated with human error. Concretely, with how passage planning and route monitoring are done. Over the cadetship enrolment on board the principles of passage planning are studied and analysed. The voyage from sakai (japan) to point fortin (trinidad and tobago) is elaborated and monitored step by step to promote deck officer cadets the acquisition of these competences. Additionally, this thesis contributes with an assessment of vessel performance on safety matters and economic and environmental costs

STUDIES ON THE NONLINEAR INTERACTIONS ASSOCIATED WITH MOORED SEMI SUBMERSIBLE OFFSHORE PLATFORMS

The design of moored semi submersible systems constitutes a challenging engineering problem in which, the platform offset, stability, payload and system-optimized cost requirements are to be met simultaneously. This problem is complicated by the incomplete understanding of the nonlinearities associated with the multiple interactions such as wave to wave, wave to platform, platform to mooring, fluid to mooring and mooring to seabed. In this study, an attempt has been made to probe into these nonlinearities through numerical, experimental, and parametric studies. In the numerical study, moored semi submersibles were analyzed in the time domain. The dynamic equilibrium conditions were satisfied through a set of coupled nonlinear differential equations for the six DOF motions. For representing the platform to mooring nonlinear interactions, the 6x6 mooring stiffness matrix was derived based on the mooring stiffness and on the fairlead coordinates relative to the structure CG. For the evaluation of the slow frequency horizontal motions of the platform, the second order wave forces resulting from the second order temporal acceleration and the structural first order motions were formulated. For the assessment of the fluid to mooring and mooring to seabed nonlinear interactions, a deterministic approach for the dynamic analysis of a multi-component mooring line was formulated. The floater motion responses were considered as the mooring line upper boundary conditions. Lumped parameter approach was adopted for the mooring line modeling. Mooring to seabed nonlinear interactions were modeled assuming that the mooring line rested on an elastic dissipative foundation. A numerical dynamic analysis method in the time domain was developed and results for various mooring lines partially lying on different soils were validated by conducting a comparative study against published results. The contribution of the soil characteristics of the seabed to the dynamic behavior of mooring line was investigated for different types of soil. Two phases of experimental studies were conducted to provide benchmark data for validating the numerical methods. In the first phase, the seakeeping performance of a semi submersible with eight circular columns was studied. The model was built to scale of 1:100 using Froud’s law of similitude. The tests were conducted for head, beam and quartering seas. In the second phase, a semi submersible with six circular columns was modeled using the same scale as for the first semi submersible. Linear mass-spring system was arranged to facilitate measurements of the horizontal drift forces. The system natural periods, still water damping, nonlinear viscous damping, drag coefficient and inertia coefficient information were evaluated from the free decay tests. Seakeeping tests were conducted for head and beam model orientations. The measured drift forces were compared to available formulae in the literature to assess the available semi-empirical methods for evaluation these forces. In both experimental phases, twin-hulled conventional semi submersibles were considered. By comparing the results of the numerical and experimental models, the validity of the numerical method was established. Based on the validated numerical algorithm, a number of parametric studies were conducted for investigating the contributions of various design parameters on the dynamics of moored semi submersibles. The effects of pretension, mooring line configuration, clump weight, cable unit weight, elongation, breaking strength and pretension angle on the behavior of multi-component mooring line, were investigated by using an implicit iterative solution of the catenary equations. On the other hand, using linearized frequency domain analysis, the contributions of platform payload, platform dimensions, number of columns, number of mooring lines, the wave environment mathematical model, the wave characteristics and the operating (intact or damage) conditions to the responses of moored semi submersibles were investigated. The experimental and published results verified the efficiency of the developed numerical model for prediction of the wave frequency and low frequency motions and mooring dynamic tension responses of the semi submersible. Moreover, experimental results indicated that in addition to the modeling of the mooring system stiffness, typical or hybrid modeling of the mooring system and attachments are necessary for the critical assessment of the mooring system damaged conditions

Frequency and time domain motion and mooring analyses for a FPSO operating in deep water

An investigation on the motion responses of a Floating Production, Storage and Offloading (FPSO) vessel moored in irregular waves has been carried out based on both frequency- and time-domain approaches. In the frequency-domain approach a three-dimensional panel method was employed in order to calculate the first-order hydrodynamic forces and moments such as added masses, potential damping and wave excitation forces and moments and of the resulting the first-order motions and mean second-order forces and moments on the vessel in six degrees of freedom behaviour. A spectral analysis was carried out in order to estimate both the significant and the extreme values of the first-order motions. Additionally Pinkster’s approximation was used to find the mean-square values of slow drift motions, in order to calculate wave-induced extreme excursions and the resulting tensions on the mooring lines of the vessel. Two different methods were used in the time-domain approach for undertaking a mooring analysis. One method used a fast practical time-domain technique that calculates the first-order motion responses in random waves based on the frequency-domain response amplitudes and simulated seas, and also solves the uncoupled second-order motion responses of the FPSO induced by second-order forces, based on Newman’s approximation in irregular seas. The other method is by solving six coupled equations of motion based retardation functions transformed from potential damping for the FPSO and induced by the first-order and second-order wave excitations in random seas. The results of the wave-induced extreme excursions and the mooring line tensions obtained by means of the frequency- and time-domain methods are compared and discussed. As the selected FPSO is operating in deep water, the effect of the mooring line inertia may be significant. The equations of motion of line dynamics were formulated and numerically solved to investigate the importance of line dynamics for deep water mooring. Comparisons between the results of the line tensions both with and without the effects of line dynamics are made and discussed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Plastic Limit Analysis of Offshore Foundation and Anchor

This study presents the applications of plastic limit analysis to offshore foundations and anchors, including the drag embedment anchors (DEAs) for mobile offshore drilling units (MODU’s) and spudcan foundations for jack-up platforms. In deep waters, drag embedment anchors are an attractive option for mooring of semisubmersible platforms due to low installation cost and high holding capacity; on the other hand, jack-up platforms are more stable than semisubmersible platforms but only can be placed in shallow waters. The analyses of anchor capacities are developed for an idealized anchor comprising a rectangular fluke, a cylindrical shank, and a metal chain connected to the shank at the padeye. The anchor trajectory prediction during drag embedment is also developed by considering anchor behavior in conjunction with the mechanics of the anchor line. The results of simulations show that anchors approach at equilibrium condition rapidly during the embedment and both the normalized holding capacity and the anchor line uplift angle remain constants in this stage. Besides the geometry of the fluke, the properties of the shank and soil are also crucial factors in the anchor-soil interaction behavior. Partial failure of mooring systems for floating structures will subject drag anchors to loads having an appreciable component outside of the intended plane of loading. Partial failure of mooring systems during hurricanes in recent years have generated an interest in understanding drag anchor performance under these conditions. The analysis presents the simulations of three dimensional trajectories of an anchor system subjected to an out-of-plane load component. For the conditions simulated in the example analyses, the anchor experienced a modest amount of continued embedment following partial failure of the mooring system; however, the ultimate embedment and capacity of the anchor is much less than what would have developed if the anchor had continued in its original trajectory within the plane of intended loading. The analyses of the spudcan foundation of jack-up units include preloading, bearing capacity, and the displacement assessment. When the contribution of the soil moment resistance is considered, a three-stage assessment procedure is recommended: superposing environmental forces on the plot of yield surface, determining the value of yield function corresponding to the external forces, and computing the factor of safety of the spudcan. The results of the assessment may be ambiguous while the different yield functions are employed to analyze the spudcan in soft clay

Advanced Anchoring and Mooring Study

This report establishes an industry knowledge base for existing anchoring and mooring techniques as applied to wave energy conversion (WEC) devices in and around Oregon. This report on anchoring and mooring techniques is derived from the cumulative experiences of engineers and scientists with many years of experience analyzing, designing and installing structures in the ocean subjected to significant environmental forces. It is not intended to be a complete design procedure but to provide the user with practical guidance on anchors and mooring techniques and sources of reliable design information necessary to the design of WEC devices suited to the coast of Oregon

STUDIES ON THE NONLINEAR INTERACTIONS ASSOCIATED WITH MOORED SEMI SUBMERSIBLE OFFSHORE PLATFORMS

The design of moored semi submersible systems constitutes a challenging engineering problem in which, the platform offset, stability, payload and system-optimized cost requirements are to be met simultaneously. This problem is complicated by the incomplete understanding of the nonlinearities associated with the multiple interactions such as wave to wave, wave to platform, platform to mooring, fluid to mooring and mooring to seabed. In this study, an attempt has been made to probe into these nonlinearities through numerical, experimental, and parametric studies. In the numerical study, moored semi submersibles were analyzed in the time domain. The dynamic equilibrium conditions were satisfied through a set of coupled nonlinear differential equations for the six DOF motions. For representing the platform to mooring nonlinear interactions, the 6x6 mooring stiffness matrix was derived based on the mooring stiffness and on the fairlead coordinates relative to the structure CG. For the evaluation of the slow frequency horizontal motions of the platform, the second order wave forces resulting from the second order temporal acceleration and the structural first order motions were formulated. For the assessment of the fluid to mooring and mooring to seabed nonlinear interactions, a deterministic approach for the dynamic analysis of a multi-component mooring line was formulated. The floater motion responses were considered as the mooring line upper boundary conditions. Lumped parameter approach was adopted for the mooring line modeling. Mooring to seabed nonlinear interactions were modeled assuming that the mooring line rested on an elastic dissipative foundation. A numerical dynamic analysis method in the time domain was developed and results for various mooring lines partially lying on different soils were validated by conducting a comparative study against published results. The contribution of the soil characteristics of the seabed to the dynamic behavior of mooring line was investigated for different types of soil. Two phases of experimental studies were conducted to provide benchmark data for validating the numerical methods. In the first phase, the seakeeping performance of a semi submersible with eight circular columns was studied. The model was built to scale of 1:100 using Froud’s law of similitude. The tests were conducted for head, beam and quartering seas. In the second phase, a semi submersible with six circular columns was modeled using the same scale as for the first semi submersible. Linear mass-spring system was arranged to facilitate measurements of the horizontal drift forces. The system natural periods, still water damping, nonlinear viscous damping, drag coefficient and inertia coefficient information were evaluated from the free decay tests. Seakeeping tests were conducted for head and beam model orientations. The measured drift forces were compared to available formulae in the literature to assess the available semi-empirical methods for evaluation these forces. In both experimental phases, twin-hulled conventional semi submersibles were considered. By comparing the results of the numerical and experimental models, the validity of the numerical method was established. Based on the validated numerical algorithm, a number of parametric studies were conducted for investigating the contributions of various design parameters on the dynamics of moored semi submersibles. The effects of pretension, mooring line configuration, clump weight, cable unit weight, elongation, breaking strength and pretension angle on the behavior of multi-component mooring line, were investigated by using an implicit iterative solution of the catenary equations. On the other hand, using linearized frequency domain analysis, the contributions of platform payload, platform dimensions, number of columns, number of mooring lines, the wave environment mathematical model, the wave characteristics and the operating (intact or damage) conditions to the responses of moored semi submersibles were investigated. The experimental and published results verified the efficiency of the developed numerical model for prediction of the wave frequency and low frequency motions and mooring dynamic tension responses of the semi submersible. Moreover, experimental results indicated that in addition to the modeling of the mooring system stiffness, typical or hybrid modeling of the mooring system and attachments are necessary for the critical assessment of the mooring system damaged conditions

Software-in-the-Loop combined Artificial Intelligence for Optimised Design and Dynamic Performance Prediction of Floating Offshore Wind Turbines

PhD ThesisFloating Offshore Wind Turbines (FOWTs) have shown a promising future due to the goal of Net Zero emissions by 2050. However, the highly coupled nonlinear performances of FOWTs bring many challenges to the implementation of numerical and basin experimental methods in design and optimisation. This PhD project proposes an innovative method, named SADA (Software-in-the-Loop combined Artificial Intelligence Method for Dynamic Analysis of Floating Wind Turbines), to optimise the design and predict dynamic performances of FOWTs. SADA is built based on a coupled aero-hydro-servo-elastic programme DARwind and Machine Learning Algorithms. Firstly, the concept of Key Disciplinary Parameters (KDPs) is inspired by FOWT-related disciplinary theories. Secondly, DARwind will take continuous action through the Software-in-the-Loop (SIL) model to obtain more accurate prediction results. Thirdly, SADA can build data sets and analyse deep-seated physical laws of FOWTs. Then, case studies were conducted to prove the feasibility of the SADA method on the basin experiment data. The results show that the mean values of some physical quantities can be predicted by SADA with higher accuracy than the original DARwind simulation results. In addition, full-scale case studies were conducted by extending SADA to engineering applications, though some design parameters are not accessible. Furthermore, other physical quantities that cannot be obtained directly in full-scale measurement easily but are of great concern to industry can also be obtained from a more credible perspective. The proposed SADA method could benefit the wind industry by taking advantage of the numerical analysis method and AI technology. This brings a new and promising solution for overcoming the handicap impeding direct use of traditional basin experimental technology or full-scale measurement. Therefore, designers in the wind industry can optimise FOWTs designs to a higher level, thereby achieving a better method of and maintaining safe operation of FOWTs in a complex sea state

The Perceived Relationship Among Personnel Readiness, Job Performance and Work Demands A Case for Physical Ability Testing

Human Systems Integration ReportThe military screening process entails meeting general physical and cognitive standards and then primarily matching candidates with a specialization based on cognitive test scores. Little consideration is given to the physical abilities required to perform tasks in that specialization. An online survey was used to explore the perceived relationship among personnel readiness, job performance and work demands for Boatswains Mates (BM) and Damage Controlmen (DC). This study explored four research questions to evaluate physical ability testing. Descriptive statistics showed that the participants had a wide range of experience levels. The results from the logistic model indicated no factors were significant of evaluation trait averages. The chi-square tests showed a difference in level of physical demands in three different modes of operations for both BMs and DCs. Both groups support the use of a physical ability testing in the selection process for job placement. Efforts to develop a physical ability test for use in the selection process, a physical remediation program for those who do not meet the standards, as well as a maintenance program to verify personnel still meet physical abilities are recommendations that should be considered for future research.http://archive.org/details/theperceivedrela1094517425Lieutenant, United States NavyApproved for public release; distribution is unlimited

Measuring and modelling towline responses using GPS aided inertial navigation

The offshore towage of large floating structures has been the broad subject of research since the 1960’s. The selection of a tug to engage in a tow is based on rules laid down by class and marine warranty surveyors derived from years of experience but a rigorous assessment of these rules based on a comprehensive real world datasets has not been possible. This is principally due to the nature of these tows, usually employing tugs chartered at short notice from the spot market, the long towline lengths when under tow and the high value of the tow itself. Given the commercial implications in being able to better match a suitable tug to any given tow, this research lays down the requirements of an ideal dataset, i.e. one that has a record of towline tensions, complete 6DOF of both the tug and tow all recorded to a universal timeline, along with the seastate experienced by the tow at any given point. It then reviews the historical restrictions in gathering this data and that the key issue has been gathering the motions of the unpowered tow and recording the towline tensions.A methodology is then developed which requires no interference with the towline and draws upon Kalman filters for optimal state estimation of the tug and tow’s position and attitude in 3D space driving a lumped mass simulation of the towline coded in MatLab. The stiffness properties of key elements of the towline are assessed by FEA and observations made on areas where normal industry practice’s may be lacking. Observations on advances in sensor technology as well as other areas for development are then made that provide fertile areas for further research. Finally the full code base for a MatLab, lumped mass simulator is presented in an appendix for future use.The offshore towage of large floating structures has been the broad subject of research since the 1960’s. The selection of a tug to engage in a tow is based on rules laid down by class and marine warranty surveyors derived from years of experience but a rigorous assessment of these rules based on a comprehensive real world datasets has not been possible. This is principally due to the nature of these tows, usually employing tugs chartered at short notice from the spot market, the long towline lengths when under tow and the high value of the tow itself. Given the commercial implications in being able to better match a suitable tug to any given tow, this research lays down the requirements of an ideal dataset, i.e. one that has a record of towline tensions, complete 6DOF of both the tug and tow all recorded to a universal timeline, along with the seastate experienced by the tow at any given point. It then reviews the historical restrictions in gathering this data and that the key issue has been gathering the motions of the unpowered tow and recording the towline tensions.A methodology is then developed which requires no interference with the towline and draws upon Kalman filters for optimal state estimation of the tug and tow’s position and attitude in 3D space driving a lumped mass simulation of the towline coded in MatLab. The stiffness properties of key elements of the towline are assessed by FEA and observations made on areas where normal industry practice’s may be lacking. Observations on advances in sensor technology as well as other areas for development are then made that provide fertile areas for further research. Finally the full code base for a MatLab, lumped mass simulator is presented in an appendix for future use